Block

A block is a record in the block chain that contains and confirms many waiting transactions. Roughly every 10 minutes, on average, a new block including transactions is appended to the block chain through mining.

Blocks are found in the Bitcoin block chain. Blocks connect all transactions together. Transactions are combined into single blocks and are verified every ten minutes through mining. Each subsequent block strengthens the verification of the previous blocks, making it impossible to double spend bitcoin transactions (see double spend below).

This is the heart of the Bitcoin system. Bitcoin is essentially an open ledger accounting system. Bitcoin transactions are broadcast to the network when they are made and then are recorded in a block by the miner who solved the most recent Bitcoin math problem. One block is like one page from that ledger, showing recent transactions that the network agrees are valid. A block is a collection of transaction data, and one of the fundamental elements of cryptocurrency. A block is a data structure that consists of a block header and a merkle tree of transactions. Each block (except for the genesis block) references one previous block and thereby forms a tree called the blockchain . A block is therefore a group of transactions with a timestamp and a proof-of-work attached. As transactions are made, the information is collected. When the gathered data reaches a predetermined size, it is bundled as a block. As soon as possible after a block is created, it is processed by investors for transaction verification in a process known as mining . The point of bitcoin mining is to create blocks. The creator of a block is rewarded with bitcoins, the number of which decreases over time. The block creator is also awarded any transaction fees attached to the transactions included in the block. Eventually new blocks will stop creating bitcoins altogether and miners will be rewarded solely through transaction fees. In order for a transaction to be confirmed its various components must be validated and checked against double spending . Once verified, transactions are incorporated in frequently issued official records called blocks. Anyone is allowed to create a block. In fact, two incentives are offered to attract verifiers to compete for block creation; the collection of fees and the minting of new coins. Transactions become effective when they have been referenced in a block, which serves as the official record of executed transactions. Transactions can only be listed in a block if they satisfy such conditions as valid timestamping and absence of double spending. A block consists of one “ coinbase ” minting transaction, zero or more regular spending transactions, a computational proof of work, and a reference to the chronologically prior block. Thus the blocks form a singly linked “blockchain” rooted in Nakamoto’s genesis block whose hash is hardcoded in the software. The regular creation of new blocks serves the dual purpose of ensuring the timely vetting of new transactions and the creation of new coins, all in a decentralized process driven by economic incentives (the minting of new coins and the collection of fees) balanced by computational costs. A feedback mechanism ensures an average block creation interval of ten minutes across the entire network. Each block includes the difficult-to-produce verification hash of the previous block. This allows each subsequent block to be linked to all previous blocks.

A block is a package of data that contains zero or more transactions, the hash of the previous block (“parent”), and optionally other data. The total set of blocks, with every block except for the initial “genesis block” containing the hash of its parent, is called the blockchain and contains the entire transaction history of a network. Note that some blockchain-based cryptocurrencies use the word “ledger” instead of blockchain; the two are roughly equivalent, although in systems that use the term “ledger” each block generally contains a full copy of the current state (e.g. currency balances, partially fulfilled contracts, registrations) of every account allowing users to discard outdated historical data.